/Engine/Source/Runtime/Experimental/Chaos/Public/PhysicsProxy/ClusterUnionPhysicsProxy.h
The mismatch here is fine since we really only need to sync a few properties between the PT and the GT.
typedef [TPBDRigidParticle](API\Runtime\Chaos\Chaos\TPBDRigidParticle)< [FReal](API\Runtime\ChaosCore\Chaos\FReal), 3 > FExternalParticle